1. Field of the Invention
The present invention relates to the field of flat panel displaying, and in particular to a backlight module and a liquid crystal display device using the backlight module.
2. The Related Arts
Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications, such as mobile phones, personal digital assistants (PDAs), digital cameras, computer monitors, and notebook computer screens.
Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise an enclosure, a liquid crystal panel arranged in the enclosure, and a backlight module mounted in the enclosure. The structure of a conventional liquid crystal panel is composed of a color filter (CF) substrate, a thin-film transistor (TFT) array substrate, and a liquid crystal layer arranged between the two substrates and the principle of operation is that a driving voltage is applied to the two glass substrates to control rotation of the liquid crystal molecules of the liquid crystal layer in order to refract out light emitting from the backlight module to generate images. Since the liquid crystal panel itself does not emit light, light must be provided from the backlight module in order to normally display images. Thus, the backlight module is one of the key components of the liquid crystal displays. The backlight modules can be classified in two types, namely a side-edge backlight module and a direct backlight module, according to the site where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the backside of the liquid crystal panel to form a planar light source directly supplied to the liquid crystal display panel. The side-edge backlight module comprises an LED light bar, serving as a backlight source, which is arranged at an edge of a backplane to be located rearward of one side of the liquid crystal display panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face at one side of the light guide plate and is projected out of a light emergence face of the light guide plate, after being reflected and diffused, to pass through an optic film assembly so as to form a planar light source for the liquid crystal panel.
Referring to FIG. 1, a cross-sectional view is given to show a conventional side-edge backlight module, which comprises: a backplane 100, a light guide plate 300 arranged in the backplane 100, and a backlight source 500 arranged inside the backplane 100 and located beside the light guide plate 300. The backlight source 500 emits light that is converted by the light guide plate 300 into a planar light source supplied to a liquid crystal display panel.
Since the liquid guide plate provides the function of converting a linear light source into a planar light source, the positioning of the light guide plate is of vital importance. Heretofore, the light guide plate is fixed in a backplane by screws. When the light guide plate undergoes expansion resulting from heating or contraction resulting from cooling or is subjected to impacts resulting from external forces, fixing through screws may not provide good cushioning to the expansion or stresses so that the light guide plate may be damaged and the quality of the backlight module affected.